OBJECTIVES: The aim of this study was to measure the regional bond strength of all-in-one adhesives under the effect of hydrostatic pressure of dentin substrate, by means of the micro tensile method. METHODS: Human caries-free third molars were randomly divided into two groups for bonding: Group 1--no pulpal pressure and Group 2--pulpal pressure of 20 cm H2O. Clearfil tri-S Bond (Kuraray), G-BOND (GC) or Adper Prompt L-Pop (3M) adhesive resins systems were applied to the cut dentin surfaces and the teeth were restored with Clearfil AP-X resin composite (Kuraray). After 24 h in water at 37 degrees C, the specimens were sectioned into 0.7 mm thick slabs and divided into three regional subgroups according to the remaining dentin thickness as follows: pulp horn, center, and periphery. The slabs were then trimmed and shaped for micro-tensile bond testing at a crosshead of 1 mm/min. The data were analyzed with ANOVA and Tukey's HSD test at a confidence level of 95%.
RESULTS:
Tensile bond strength to dentin, µTBS: MPa±SD (same letters represent no significance)
|
|
Group I (Pulpal pressure=0) |
Group II (Pulpal pressure=20 cmH2O) |
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|
|
tri-SB |
G-BOND |
AdperLP |
tri-SB |
G-BOND |
AdperLP |
|
Pulp horn |
20.8±7.7 |
27.4±9.8 |
19.0±15.3 |
19.5±11.1 |
28.5±1.0 |
4.9±10.2 |
|
Center |
31.9±10.7 |
30.8±15.1 |
31.1±17.1 |
22.1±11.6 |
32.2±15.7 |
7.7±10.2 |
|
Periphery |
34.3±12.3 |
39.3±15.0 |
37.2±22.9 |
18.4±10.2 |
37.4±1.0 |
12.6±18.9 |
For G-BOND, no significant regional difference was found between Group 1 and Group 2. In contrast, the bond strength of Adper Prompt L-Pop under the pulpal pressure was significantly lower than the bond strengths in the absence of pulpal pressure for all regions. For tri-S Bond, there were no regional differences in bond strength in the absence of a pulpal pressure but in the presence of pulpal pressure, the bond strength of center and periphery regions fell significantly. Conclusion: Effect of pulpal pressure on regional bond strengths was different between adhesive systems tested.